Based on the information you've provided and the knowledge sources available, this difference in authentication placement could indeed be causing the issue you're experiencing. Let's explore this further: 1. Authentication Header vs Body: You're correct in observing that Postman is sending the authentication in the header, while Airbyte seems to be including it in the body. This discrepancy could be the root cause of your 401 Unauthorized error. 2. Airbyte OAuth Configuration: According to the [Authentication documentation](https://docs.airbyte.com/connector-development/config-based/understanding-the-yaml-file/authentication), Airbyte supports various authentication methods, including OAuth. However, the default implementation might not match your API's requirements. 3. Custom Header Requirement: Some APIs require specific header configurations. For instance, in a [Github issue discussion](https://github.com/airbytehq/airbyte/issues/46094), a user mentioned needing an empty body and a custom authorization header:

Authorization: Zoho-oauthtoken {{ config["oauth_access_token"] }}

4. Potential Solution: You might need to customize the OAuth implementation in Airbyte to match your API's requirements. This could involve: a. Modifying the authentication configuration to use a custom header instead of including credentials in the body. b. Ensuring the OAuth token is correctly placed in the header of each request. 5. Limitations of UI Connector Builder: It's worth noting that a contributor in the same Github issue mentioned that such customization might not be possible with the UI connector builder or low-code approach. You might need to consider developing a custom connector if the UI builder doesn't provide enough flexibility. To resolve this issue, you could try: 1. Checking if there's an option in the Airbyte Connector Builder to specify custom headers for authentication. 2. If possible, modify the YAML configuration to include the OAuth token in the header instead of the body. 3. If these options aren't available, you might need to consider developing a custom connector that allows for more precise control over the authentication process. If you continue to face issues, it would be helpful to share more details about the specific API you're working with and any error messages you receive. Additionally, consulting Airbyte's documentation or reaching out to their support channels might provide more targeted assistance for your specific use case.